A friend asked me, in terms of Bayesian
probability, what are the chances that Jesus actually rose from the dead? My response:
I'll write this in the most accessible way I can. Bayesian probability helps us update our beliefs based on new evidence - so the more supporting evidence we have, the more rational it becomes to believe a claim. We have to apply some caution when using Bayesian probability in relation to God, because Bayesian probability typically requires a prior probability (P(H)) that is determined independently of the specific evidence being evaluated (this is known as a common prior) - and this is tricky without a clear statistical or empirical basis to quantify it (it's not like calculating the probability of rolling a 12 with two dice). But as long as we keep the above caveats in mind, we can have a go. So we are considering four primary things:
P(H | E) = Probability of the hypothesis
(resurrection) given the evidence
P(E | H) = Probability of the evidence if the
resurrection happened
P(H) = Prior probability of the resurrection
(before considering the evidence)
P(E) = Probability of the evidence occurring in
general
P is probability, H is hypothesis and E is evidence - and obviously from a naturalistic perspective, if there is no God, the probability that anyone would rise from the dead is near-zero. But Bayesian probability from a scientific perspective changes radically as/if we know there is a God who loves us, and was willing to suffer and die for us, and rise from the dead to give us eternal life. Therefore, this won't be easily measurable in terms of the Bayesian ratio of favourable cases to total possible cases. The P(H) (prior probability of resurrection) is extremely low in naturalistic terms, but high if we believe Jesus is who He says He is; and the P(E | H) (likelihood of the evidence if resurrection happened) is high, because if it happened it would be the most remarkable, earth-shattering, life changing event in world history (and it is).
I'd also add that, if there is a God, we’d expect Him to make Himself known – which is what Christianity claims. It’s the only religion which claims with any justification that God Himself has made Himself known in person (in Christ, and through the Holy Spirit). And we know from 1 Corinthians 15 that the resurrected Christ appeared to over 500 people. It's not easily conceivable that Christianity would have been the biggest and most important alteration of human history if Christ had not died and risen, especially under the conditions and culture of the time, where it was very much not in people's interest to promote Christianity, and in many cases, doing so presented a danger to their own life. In fact, from the impression I get from reading New Testament history over the years, I think I would be bold enough to state it even more stridently - not only did Christianity spread, but in worldly terms it did so among people who had little to gain and so much to lose - domestically, socially, politically, physically, you name it. Unlike other movements that thrived through military conquest or political weight, Christianity grew in the most remarkable way - through self-sacrifice and love, radically defying the patterns of history that went before or since.
Moreover, in terms of the credibility of what Jesus actually said and did, many leaders and cult figures have deceived many willing adherents over the years, but Jesus demonstrated all the opposite traits of typical false leaders. False leaders usually seek power, status, and control in a way that serves themselves. Jesus showed His humility and power by serving others, giving up His life for us. False leaders use lies, manipulation and falsehoods to maintain their power and influence, but Jesus spoke only the truth. False leaders operate through promoting division, separateness and fear, but Jesus preached love, inclusivity and togetherness. Jesus spoke the wisest and truest words ever spoken about God, because He is God. He is unique in history and in personally revealing God's love to humankind, and that is why Christianity changed the world in the way that it did, in a way that's unparalleled in human history. Not only is there nothing like it, there is nothing that can even be spoke of using the same type of language. It's as different from the false religions as the sun is different to a candle.
So, in summary, Christians have confidence that God exists, that He has revealed Himself in history, that He loves us, that He was willing to die for us, and that when all the evidence for His resurrection is considered in light of that (namely, the sheer weight of historical testimony, the transformation of Jesus’ followers, and the unparalleled impact of Christianity), Bayesian reasoning points to the resurrection being a historical event, not a made up one. And, of course, this logic works in reverse too - if it was merely made up, it would be far more improbable, contrived, historically unexplainable and philosophically unsatisfying than if it really happened.
